BOSTON — A federal judge has ruled that a Boston University student violated copyright laws when he swapped music online, paving the way for a jury to begin considering damagestoday.

Joel Tenenbaum, 25, of Providence, R.I., admitted on the witness stand Thursday that he downloaded and shared hundreds of songs by Nirvana, Green Day, The Smashing Pumpkins and other artists. The recording industry focused on only 30 songs in the case, the nation’s second music-downloading lawsuit against an individual to go to trial.

U.S. District Judge Nancy Gertner in Boston ruled late Thursday that the only issue for the jury now is whether his infringement was willful, and how much in damage to award four recording labels that sued him over the illegal file-sharing.

Under federal law, the recording companies are entitled to $750 to $30,000 per infringement but the law allows the jury to raise that to as much as $150,000 per track if it finds the infringements were willful.

Last month, a federal jury in Minneapolis ruled a Minnesota woman must pay $1.92 million, or $80,000 on each of 24 songs, after concluding Jammie Thomas-Rasset, 32, willfully violated the copyrights on those tunes.

The music industry has typically offered to settle such cases for about $5,000, though it has said that it stopped filing such lawsuits last August and is instead working with Internet service providers to fight the worst offenders. Cases already filed, however, are proceeding to trial.

On the witness stand, Tenenbaum acknowledged that he had downloaded more than 800 songs since 1999 and admitted that he lied in pretrial depositions when he said that his two sisters, friends and others may have been responsible for downloading the songs to his computer.

Under questioning from his own lawyer, Harvard Law School professor Charles Nesson, Tenenbaum said he now takes responsibility for the illegal swapping.

“I used the computer. I uploaded, I downloaded music … I did it,” Tenenbaum said.

His testimony contrasted with the tactic used by Thomas-Rasset. Even after the jury’s verdict, she declared, “There’s no way they’re ever going to get that.”

In opening arguments Tuesday, Nesson said Tenenbaum “was a kid who did what kids do” and should not be harshly penalized for technological advances that he said recording companies have been slow to embrace.

But Tim Reynolds, one of the lawyers representing the recording industry, said then that song-swappers like Tenenbaum take a significant toll on the recording industry’s revenues and on backup singers, sound engineers and other people who make a living in music.